(1) Field of the Invention
The present invention relates to methods used to fabricate semiconductor devices, and more specifically to a method used to increase the performance of metal oxide semiconductor field effect transistor (MOSFET), and of vertical bipolar devices, via use of specific trench isolation (TI), fill materials.
(2) Description of Prior Art
Formation of strained, silicon channel regions in MOSFET devices, can enhance carrier transport properties and thus improve device performance for MOSFET devices. Various approaches have been applied in attempts to introduce strain in a MOSFET channel region. Channel regions with the desired strain have been obtained in strained silicon layers, when the silicon layer is grown overlying relaxed semiconductor alloy layers such as silicon-germanium, or silicon-germanium-carbon. However the above approach requires the growth of the semiconductor alloy layer, followed by the epitaxial growth of the strained silicon layer, both adding significant cost and process complexity to the device process sequences used to fabricate MOSFET devices.
This invention will describe methods and layouts, allowing both biaxial compressive strain and tensile strain to be formed in channel regions for MOSFET devices, as well as in base regions of vertical bipolar devices. This is accomplished without the use of semiconductor alloy layers, featuring strain induced in silicon regions located adjacent to STI regions which have been filled with specific materials which allow the desired silicon strain to be realized. Prior art, such as Kim et al, in U.S. Pat. No. 6,297,128 B1, Park et al, in U.S. Pat. No. 6,037,237, Yagishita et al, in U.S. Pat. No. 6,310,367 B1, and Kuo, in U.S. Pat. No. 5,946,562, describe methods of forming: STI regions: some with composite fill layers; some with strained silicon channel regions; and some using the combination of strained channel and STI regions. However none of the above prior art offer the process or layout, described in the present invention in which strained silicon regions are formed as a result of the material used to fill adjacent shallow trench shapes.